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28 June 2011

I recently had to install Fedora on a Dell XPS 15. Unfortunately while installation wasn't a problem getting it to boot for the first time was. I'd previously tried Fedora 14 and found much the same result and was hoping that the issue would just be gone in Fedora 15.

During boot I kept having problems with synchronisation with a number of different error messages like "scheduling while atomic", and "fatal exception in interrupt". This always inevitably lead to the same result Kernel Panic, although a couple of times it did tell me that it was trying by "fixing recursive fault but reboot is needed" although this never seemed to make a difference.

I had an idea that it was one of the kernel modules causing the problem, but I had no idea which, and so by trial and error I eventually determined that it was iwlagn. This fix is then reasonably simple just blacklist the module like so:

#vi /etc/blacklist.conf
+ blacklist iwlagn

Once black listed I found that Fedora booted successfully and I was able to log in.

There is one slight issue that I neglected to mention in the above is how do you manage to edit blacklist.conf, when you can't boot the system. I had a live Ubuntu CD around which I found worked and it was simply a matter of mounting the partition and editing the file.

24 June 2011

Why would you want to do this? I wanted support for Intel TBB which adds threading support to OpenCV and is not included in the standard build. Also I had problems with my web cam with the standard build and so also had to patch the code.

Download and install Intel TBB, in my case I installed it to: "C:/Development/Intel/TBB/Include/"

Download OpenCV 2.2 source code.

Apply the source code changes listed after this section. (Note these are not optimal, and some could be better specified with command link options, but I had trouble specifying a few command line options and this code was the first working version I came up with).

Open a command prompt with the Visual Studio paths and variables defined. It will be called something like "Visual Studio Command Prompt (2010)"

On Windows the source code can be configured using the following command line: # cmake -D CMAKE_BUILD_TYPE=RELEASE ..\
or# cmake -D CMAKE_BUILD_TYPE=DEBUG ..\Note: The way you need to specify command line arguments varys between versions of windows, see here for more details: http://opencv.willowgarage.com/wiki/InstallGuide#Build

Then build:# nmake

Link to the libraries from within your code, linking the *d.lib versions with the debug code and *.lib versions with release code.

Copy the *.dlls for both OpenCV and IntelTBB into the applications output directory.

Note I also found the following option worked for those who don’t link using nmake, but I haven’t tested it beyond configuring the build process:# cmake -D CMAKE_BUILD_TYPE=RELEASE -G"Visual Studio 10" ../